1. Field of the Invention
This invention relates to a vibration wave driving apparatus having an output shaft.
2. Related Background Art
Several vibration motors (vibration wave driving apparatuses) having output shafts are known. For example, as shown in FIG. 4 of the accompanying drawings, there is a motor disclosed in Japanese Patent Application Laid-Open No. 5-38170. This motor is such that piezoelectric elements 142 and 144 are disposed between metallic blocks 150 and 152 as hollow cylindrical elastic members and the two metallic blocks 150 and 152 are coupled together into a vibration member 140 by a cylindrical coupling bolt 154 disposed on the inner peripheral side of these metallic blocks 150 and 152. On the other hand, a motor housing (outer case) 170 is such that the cylindrical portion of the central portion of a motor forms a motor supporting portion and a bearing 172 is disposed in the motor supporting portion and supports an output shaft 134, and a ring-shaped flange portion 175 provided on the inner diametral portion of a coupling bolt 154 is fixed to the motor supporting portion and supports the vibration member 140. Also, a rotor portion 130 as a contact member is disposed on one side of the vibration member 140, and this rotor portion 130 is of a construction in which a spring 133 is disposed between a fixed rotor body (disc) 132 and a support plate 136 in the direction of rotation of the output shaft 134, and the rotor body 132 is brought into pressure contact with the end surface of the metallic block 152 by the spring force of a spring 133.
In the above-described example of the prior art, however, only a single bearing is used. Therefore, when a force is applied to the output shaft from a radial side, the output shaft may become inclined with the aforementioned bearing acting as a fulcrum, whereby the rotor portion deviates relative to the vibration member. As a result, a frictional contact state of a rotor contact surface 160, where the rotor body 132 contacts the metallic block 152, becomes non-uniform; this may result in problems such as a reduction in the efficiency of the motor, the occurrence of noise, and wear of the contact surface (a reduction in the life of the motor).
One aspect of this invention is to provide a vibration type driving apparatus in which a vibration member is supported in a case thereof by a support member, an output shaft is supported by bearings at opposite end portions of the case, where the output shaft is extended through a through-hole in the axial center portions of the vibration member and a rotating member, and the through-hole of the vibration member is used as a sliding bearing for the output shaft. In this manner, the motor may be stably driven even if extraneous forces act on the output shaft from various directions.